Download Bone Mineral Density Scan - I

Bone Mineral Density Scan
Patient Information
What is a Bone Mineral Density Scan?
A dual-energy X-ray absorptiometry scan (DEXA), or bone density
scan, is a special type of X-ray that measures bone mineral density
(BMD). It provides information about bone strength or fragility
and the risk of fractures or broken bones. A higher density generally
indicates a lower risk of fracture.
The spine and one or both hips are routinely scanned. The forearm
might also be scanned if either the hip or spine is unavailable
(usually due to surgery). As any condition affecting bone density
|tends to affect the whole skeleton, a snapshot of a few sites
is sufficient to establish the overall bone density.
The most important aspect of a DEXA scan is to position the hips and
spine in the same way each time you are scanned, so that results
are accurate and comparable at each visit. To achieve this, when
scanning the spine, a cushioned box will be placed under your knees.
The cushioned box allows the small of your back or lower spine to
lie flat on the table. To scan the hip, this box is removed and a frame
made up of a flat sheet of Perspex with a triangle at one end will be
placed between your feet.
The frame allows the leg being scanned to be positioned accurately.
The foot is strapped to the triangle by Velcro, and the knee can also
be held in place by a Velcro strap to keep the leg still. Generally,
neither of these positioning manoeuvres are uncomfortable or painful.
The BMD at the hip and spine has been shown to be the best
way of predicting the risk of fracture.
Are there any after effects of a BMD Scan?
On some occasions, scans of the forearm may also be obtained.
There are no after effects of a BMD Scan.
Why would my doctor refer me to have this
procedure?
How long does a BMD Scan take?
You might be referred for this test if you have:
• a medical condition that could weaken your bones
• had recent fracture after a minor injury or fall, that would
not have broken this bone in other people
• an X-ray image or picture taken for another reason which has shown
that the vertebrae in your spine are weakened and losing height.
The most common cause for this is osteoporosis, which
is a common condition that increases with age. It is a major cause
of weak bones, causing fractures resulting from minor injury, which
is preventable with treatment. Osteoporosis, in the absence of
fracture, has no symptoms. A number of medical conditions and
medications can increase bone loss, making it important to diagnose
osteoporosis early, to prevent fractures from occurring. The DEXA
scan measures the bone mineral content and provides information
to your doctor as to whether you have lost a small amount of bone
(osteopenia) or a more significant amount (osteoporosis), compared
with a young normal population, and people of the same age and sex
as you. This informs your doctor about your risk of having a fracture,
and assists in monitoring bone loss and in planning any preventative
therapy or medical treatment.
How do I prepare for a BMD Scan?
No preparation is required for this procedure. You do not need to fast,
and you can take all your medications as usual. It is helpful, but not
essential, to wear loose fitting clothing without metal buttons, buckles,
fasteners or zippers, as metal objects interfere with the scan. A gown
or sheet is provided if clothing needs to be removed.
A DEXA scan does involve a very small dose of radiation, which
makes this test unsuitable for women who are, or might be, pregnant.
If you have had spinal surgery, particularly with metallic implants,
or hip surgery (hip replacements, screws or pins) you will need
to inform the radiographer carrying out the scan, who might decide
to avoid that area.
Any radiological investigation using contrast media (Barium
enemas, IVP’s and CT scans) or nuclear medicine test might interfere
with the accuracy of the DEXA scan if carried out within the last week.
This can usually be discussed at the time you book your DEXA
scan appointment.
What happens during a BMD Scan?
On arrival for your DEXA scan, your height and weight will be
measured. This allows the computer to generate information
about your bone density.
A BMD scan varies between individual scanning machines,
and can take from 10 minutes to 30 minutes.
What are the risks of a BMD Scan?
Generally, the risks of a BMD scan by DEXA are very small.
The radiation doses used are extremely small and significantly
less than those used in normal X-ray images, allowing the
radiographer to remain in the room, without the need for
lead protection.
What are the benefits of a BMD Scan?
A DEXA scan is currently the best test for measuring the amount
of bone (density) in the spine, hip or wrist. The result is a comparison
of your bone density with both the young normal population (of the
same sex), and to an age- and sex-matched population. The BMD
provides information about fracture risk and bone loss. It can be
used to monitor response to treatment, with the usual frequency
of scanning being 2 years.
More accurate assessment of BMD is obtained when the
measurements are repeated at the same location and on the
same machine.
Who does the BMD Scan?
A radiographer (medical imaging technologist) skilled in DEXA scans
will carry out the scan, and ensure you are positioned correctly and
you are comfortable. In most instances the radiographer will remain
in the room with you for the duration of the scan.
The images taken by the radiographer will be reviewed
by a radiologist (specialist doctor), and a written report provided
to your referring doctor.
How do I get my results?
Your doctor will receive a written report on your test as soon
as is practicable.
It is very important that you discuss the results with the doctor
whom referred you so that they can explain what the results
mean for you.
This information is credited to Inside Radiology, Royal Australian
and New Zealand College of Radiology (RANZCR).
insideradiology.com.au
June 2014
i-medradiology.com.au